Terminal construction



1969 H. A. M INTOSH ETAL 3,462,316

TERMINAL CONSTRUCTION Filed Sept. 20, 1965 fws/wafis 29 I HAOLD A. MIWWSM,

5 flaw w M. WAG/reg,

United States Patent US. Cl. 136-230 4 Claims ABSTRACT OF THE DISCLOSUREA thermocouple terminal including a terminal member having alongitudinal passageway and a radially extending recess opening at oneend of said passageway. A conductor received by said terminal member inlocking engagement within said passageway and recess to preventrotational and longitudinal movement of said conductor relative to saidterminal member.

This invention relates to terminal construction and more particularly toan improved mechanical and electrical joint between a thermocoupleconductor and the terminal member of the thermocouple.

Inner and outer coaxial conductors electrically insulated from eachother are often used to electrically connect a thermocouple to anexternal circuit. The inner conductor is attached to a terminal memberwhich in turn is secured to a contact of the external circuit. Asuitable socket may be provided in the external circuit to receive theterminal member.

Problems have arisen in connection with the securing of the terminalmember to the thermocouple conductor. In some instances, the terminalmember and conductor joint have failed structurally, thereby destroyingthe electrical connection, while in other instances the structuralconnection has remained substantially intact but the electricalconnection has deteriorated. In either instance, the thermocouplebecomes substantially electrically isolated from the external circuitand is disabled from performing its important functions.

Accordingly, an object of this invention is to provide an improvedelectrical and mechanical joint between a terminal member and athermocouple conductor.

Another object of this invention is to use interlocking means andconductive bonding material to secure a terminal member to athermocouple conductor.

Another object of this invention is to provide an improved terminalconstruction which includes a terminal member having a passagewaytherethrough and a laterally extending locking recess opening at thepassageway, an elongated electrical conductor in said passageway andhaving a locking portion extending laterally into the locking recess,and conductive bonding material for bonding the elongated electricalconductor to the terminal member. The locking portion of the conductorengages the walls of the locking recess to prevent relative rotationtherebetween and the prevent relative translation therebetween in atleast one direction. The conductive bonding material further strengthensthe conductorterminal member joint and also forms a portion of theterminal for the thermocouple. Thus, the combination of structuralinterlocking means and conductive bonding material forms a strong jointhaving a long useful life.

Another object of this invention is to provide a locking recess whichopens at the passageway of the terminal member and also at one of theend faces of the terminal member. This feature of the inventionfacilitates construction in that it permits insertion of the conductorthrough the passageway of the terminal member and then bending of theend portion of the conductor into the recess.

A further object of this invention is to provide a terminal constructionin which one end of the passageway through the terminal member isenlarged so that the interior wall thereof is spaced from the elongatedelectrical conductor to define a cavity for receiving the conductivebonding material.

A particular object of this invention is to provide a thermocoupleassembly including a thermocouple; inner and outer generally coaxialconductors, the outer conductor being connectible to a first contact ofan electrical circuit, the inner conductor having a section extendingaxially beyond the outer conductor; a terminal member having first andsecond end faces and a generally longitudinal passageway extendingtherethrough to connect the end faces, the terminal member having wallsurfaces defining a generally radially extending locking recess openingat the passageway, the section of said inner conductor extending intosaid passageway from the first end face toward the second end face, thesection of the inner conductor terminating in a generally radiallyextending locking finger, the locking finger extending into said lockingrecess and being engageable with the wall surfaces thereof tosubstantially prevent relative rotation between the terminal member andthe inner conductor; insulating means for electrically insulating theouter conductor from the terminal member; and conductive bondingmaterial for bonding the inner conductor to the terminal member, thebonding material and the terminal member forming a terminal for thethermocouple.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings in which:

FIG. 1 is a side elevational view of a thermocouple assembly embodyingthe novel terminal construction of this invention;

FIG. 2 is an enlarged bottom view of the terminal construction; and

FIG. 3 is an enlarged fragmentary sectional view taken along line 3-3 inFIG. 1 and showing the terminal construction secured to a socket of anexternal circuit.

Referring to the drawing and in particular to FIG. 1 thereof, referencenumeral 11 designates a thermocouple which includes a tubular member 13of a first metal, a wire 15 of a dissimilar metal within and coaxialwith the tubular member, and a weld 17 for securing one end of the wire15 to the end of the tubular member 13 to form the hot junction of thethermocouple. A tubular connector 19 is secured to the lower end of thetubular member 13. A tube or outer conductor 21 of a conductive metalsuch as copper and having a flared lower end 23 is secured to theconnector 19. A second wire or inner conductor 25 is secured as bysoldering to the wire 15 and extends within and coaxial with the tube21. The tube 21 and the conductive wire 25 are electrically insulatedfrom each other by insulation 26 (FIG. 3). Thus, the tube 21 and thewire 25 form inner and outer coaxial conductors for carrying the currentdeveloped by the thermocouple 11 to an external circuit.

The inner conductor 25 has a section 27 (FIG. 3) which extends axiallybeyond the flared end 23 of the outer conductor 21. A cylindricalinsulating washer 29 is mounted on the section 27 of the inner conductor25 in abutting relationship with the flared end 23.

A terminal member 31 having a first end face 33, a second end face 35,and an interior wall defining an axial longitudinally extendingpassageway 3-7 is mounted on the section 27 as show in FIG. 3. Theterminal member 31 has a radially extending locking recess or slot 39which opens at the passageway 37 and at the end face 35.

The section 27 of the inner conductor 25 extends into the passageway 37from the end face 33 toward the end face 35. An end portion 41 of theinner conductor 25 is bent through approximately a 90 angle so that itextends radially into the locking recess 39 to define a locking fingerwhich terminates within the locking recess. The locking recess 39 hasgenerally opposed spaced surface areas 43 and 45 which the lockingfinger 41 engages to prevent relative rotation between the terminalmember 31 and the inner conductor 25. The surface areas 43 and 45 may beplanar or partially rounded to conform to approximately the upper onehalf of the periphery of the locking finger 41. The terminal member 31also has an upper wall or surface means 47 which defines at least aportion of the locking recess 39 and engages the locking finger 41 toprevent longitudinal movement of the locking finger toward the end face33. The upper wall 47 may be planar or rounded to mate with the portionof the locking finger 41 which is engageable therewith.

The passageway 37 includes a frusto-conical counterbore 49 extendinginwardly from the end face 35. The walls of the counterbore 49 and of aportion of the passageway 37 are spaced from the inner conductor 25 todefine a cavity 51. Conductive bonding material 53 such as solder isdisposed in the cavity 51 to bond the inner conductor 25 to the terminalmember 31. Alternatively, the inner conductor 25 may be directly bondedto the terminal member 31 as by resistance welding or cold pressureforming. Regardless of the method used to make the bond, the materialwhich flows or is worked to secure the conductor 25 and the member 31together is referred to herein as the conductive bonding material orbonding material. As shown in FIG. 3, some of the bonding material 53may enter the locking recess 39. The bonding material 53 and theterminal member 31 form a terminal for the thermocouple 11.

The terminal member 31 is preferably generally cylindrical andconstructed of a conductive metal such as brass. The end face 35 isprovided with a protruding peripheral frusto-conical surface 55. Whenthe terminal member 31 is secured to the inner conductor 25, the endface 33 abuts the insulating washer 29 thereby sandwiching the washerbetween the terminal member and the flared end 23.

The terminal structure described hereinabove may be electricallyconnected to an external circuit by a variety of devices. One suitablearrangement for securing the terminal structure to an external circuitis illustrated in FIG. 3. A conductor 57 having three axial bores 59,61, and 63 of progressively decreasing diameter is suitably secured to asupporting structure 65 by an electrically conductive terminal stem 67and an electrically conductive terminal nut 69. The terminal nut 69 hasa frusto-conical recess 71 at the upper end thereof. A terminalinsulator 73, an insulator bushing 75, and a terminal washer 77 allconstructed of insulating material electrically insulate the terminalstem 67 and the nut 69 from the conductor 57. A nut or tubular securingmeans 79 of a conductive material such as brass is slidably mounted onthe outer conductor 21. As shown in FIG. 3, the nut 79 engages theflared end 23 of the outer conductor 21 and is threadedly received bythe bore 59. Thus, the nut 79 electrically connects the outer conductor21 and the conductor 57.

The conical surface 55 on the terminal member 31 is received by thefrusto-conical recess 71 of the terminal nut 69 thereby electricallyconnecting the inner conductor 25 and the terminal stem 67. Thisrelationship is maintained by the nut 79 and the threaded bore 59. Theconductive bonding material 53 may also contact the terminal stem 67.

It is apparent therefore that an improved electrical and mechanicaljoint between the terminal member 31 and the inner conductor 25 has beenprovided. The locking finger 41 and the locking recess 39 prevent allrelative movement between the inner conductor 25 and the terminal member31 except translation of the locking finger toward the end face 35. Suchtranslation is prevented, however, by the conductive bonding material 53which rigidly holds the locking finger within the locking recess. Thus,without the addition of separate fastening means, a strong mechanicaljoint is obtained.

To facilitate construction and assembly, it is preferred that thelocking recess 39 open at the end face 35. Thus, the section 27 isinserted through the passageway 37 and then the end portion of thesection 27 is bent through approximately to form the locking finger 41which may then be slid into the locking recess. The counterbore 49provides additional volume into which the conductive bonding material 53may be deposited.

Many changes, modifications, and substitutions may be made by one havingordinary skill in the art without necessarily departing from the spiritand scope of this invention.

What is claimed is:

1. In a thermocouple assembly connectible to first and second contactsof an electrical circuit, the combination of:

a thermocouple;

a first elongated electrical conductor electrically connected to saidthermocouple and connectible to the first contact of the electricalcircuit, said elongated electrical conductor having an end portion;

a second electrical conductor electrically connected to saidthermocouple and connectible to the second contact of the electricalcircuit;

a terminal member having first and second end faces,

said terminal member having an interior wall defining a longitudinalpassageway extending through said terminal member and connecting saidend faces, said terminal member having a radially extending lockingrecess opening at said passageway, said locking recess having generallyopposed spaced surface areas;

said first elongated electrical conductor extending into said passagewayfrom said first end face toward said second end face, said end portionof said first elongated electrical conductor extending radially intosaid locking recess to define a locking finger which terminates withinsaid locking recess, said locking finger being engageable with saidgenerally opposed spaced surface areas to prevent relative rotationbetween said terminal member and said first elongated electricalconductor, at least a portion of said first elongated electricalconductor being spaced from said interior wall of said passagewayadjacent said second end face of said terminal member to define acavity;

surface means on said terminal member defining at least a portion ofsaid locking recess for engaging said locking finger to preventlongitudinal movement of said locking finger toward said first end faceof said terminal member; and

means within said cavity for securing said first elongated electricalconductor to said terminal member.

2. A combination as defined in claim 1 wherein said passageway includesa counterbore extending inwardly from said second end face of saidterminal member, the Wall of said counterbore being spaced from saidelon gated electrical conductor to define at least a portion of saidcavity.

3. In a thermocouple assembly connectible to first and second contactsof an electrical circuit, the combination of:

a thermocouple;

inner and outer generally coaxial conductors electrically connected tosaid thermocouple, said outer conductor being connectible to the firstcontact of the electrical circuit, said inner conductor having a sectionextending axially beyond said outer conductor;

first insulating means for insulating said inner conductor from saidouter conductor;

an insulating washer on said section of said inner conductor, saidwasher engaging said outer conductor;

a terminal member having first and second end faces,

a terminal member having first and second end faces,

said terminal member having an interior wall defining a longitudinalpassageway extending through said terminal member and connecting saidend faces, said terminal member having a radially extending saidterminal member having an interior wall defin- 5 locking recess openingat said passageway and at ing a longitudinal passageway extendingthrough said said second end face, said locking recess havinggenterminal member and connecting said end faces, said erally opposedspaced surface areas; terminal member having a radially extendinglocksaid elongated electrical conductor extending into said ing recessopening at said passageway and at said sec- 10 passageway from saidfirst end face toward said end end face, said locking recess havinggenerally second end face, said end portion of said elongated opposedspaced surface areas; electrical conductor extending radially into saidlocksaid section of said inner conductor extending into ing recess todefine a locking finger which terminates said passageway from said firstend face toward said within said locking recess, said locking fingerbeing second said end face, said first end face abutting engageable withsaid generally opposed spaced sursaid insulating washer, said section ofsaid inner conface areas to prevent relative rotation between saidductor having an end portion which extends radially terminal member andsaid conductor, at least a porinto said locking recess to define alocking finger tion of said conductor being spaced from the interiorwhich terminates within said locking recess, said Wall of saidpassageway adjacent said second end locking finger being engageable withsaid generally face of said terminal member to define a cavity; opposedspaced surface areas to prevent relative rosaid passageway including acounterbore extending intation between said terminal member and said in-Wardly from said second end face of said terminal ner conductor; member,the wall of said counterbore being spaced said passageway being enlargedadjacent said second from said elongated electrical conductor to defineat end face to define a cavity between said interior wall least aportion of said cavity; and said inner conductor; surface means on saidterminal member defining at surface means on said terminal memberdefining at least a portion of said locking recess for engaging least aportion of said locking recess for engaging said locking finger toprevent longitudinal movement said locking finger to preventlongitudinal movement of said locking finger toward said first end faceof of said locking finger toward said first end face of said terminalmember; and said terminal member; conductive bonding material withinsaid cavity for a deposit of solder within said cavity for bonding saidbonding said conductor to said terminal member.

inner conductor to said terminal member, said de- References Cited positand sald terminal member forming a terminal for the thermocouple; andUNITED STATES PATENTS tubular securing means on said outer conductor for1,190,524 7/1916 Douglas.

securing said terminal to the second contact of the 2,691,056 10/1954Wolff 13 223 electrical circuit. 2,755,451 7/ 1956 Smyers, 4. Terminalconstruction adapted for connection to a 2,992,402 7/1961 Thoma 13 .435

contact of an electrical circuit comprising:

an elongated electrical conductor having an end portion;

WINSTON A. DOUGLAS, Primary Examiner M. J. ANDREWS, Assistant Examiner

